JPH0661620A - Production of wiring board - Google Patents

Abstract

PURPOSE:To realize an excellent transfer of a conductive pattern by transferring a conductive pattern to a molding resin through an adhesive ink. CONSTITUTION:A resistor 2 is formed, at first, on one surface of a mold releasing film 1. Electrodes 3 are then formed at the opposite ends of the resistor 2 and thermally set. An adhesive layer 4 containing a first resin having low molecular weight, a second resin having high molecular weight, and inorganic filler, is further formed on the resistor 2 and the electrodes 3. A carrier film, on which the resistor 2, the electrodes, and the adhesive layer 4 are formed, is then transferred to an injection molding die 5. After the dies 5 are clamped, molten resin is injected through a gate 6 into a cavity 7 in order to integrate the carrier film and a molded item 8 thus obtaining a laminate. Finally, only the mold releasing film 1 is peeled off the laminate thus obtaining a resistor board 9 where the resistor 2 and the electrodes 3 are transferred through the adhesive layer 4 onto the molded item 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a wiring board having a conductive pattern such as a resistor or a wiring pattern, and more particularly, transferring a conductive pattern printed on a film to a molding resin in a mold. So-called MID (Mold
ed Interconnection Device
The present invention relates to a method of manufacturing a substrate using a method called e).

[0002]

2. Description of the Related Art FIG. 4 is an explanatory view showing a schematic process of a conventional resistance substrate manufactured by using the MID technique. First, on one surface of the release film 1 as shown in FIG.
By printing a resistance paste in which carbon powder is mixed in a binder resin and volatilizing and drying the solvent contained in the resistance paste, as shown in FIG. 4 (b), a resistor is formed on one surface of the release film 1. Form 2. Next, a silver paste in which a silver powder is mixed in a binder resin is printed on both ends of the resistor 2 to evaporate the solvent contained in the silver paste.
As shown in FIG. 4C, the electrodes 3 are formed on both ends of the resistor 2 by drying, and then these are fired.

Subsequently, the release film 1 on which the resistor 2 and the electrode 3 are formed (hereinafter, the release film in this state is referred to as a carrier film) is sent to an injection molding die 5 shown in FIG. 4 (d). After the injection molding die 5 is clamped, a molten resin is injected from the gate 6 into the cavity 7 and cooled. Thereafter, the injection molding die 5 is opened to obtain a laminate of the molded body 8 in which the molten resin is solidified and the carrier film integrated with the molded body 8 as shown in FIG. 4 (e). . Finally, when only the release film 1 is peeled off from this laminate, as shown in FIG. 4 (f), a resistance substrate 9 in which the resistors 2 and the electrodes 3 are transferred to the molded body 8 is obtained.

[0004]

The resistor 2 on the resistor substrate 9 obtained by the MID technique as described above is formed because the smoothness of the release film 1 becomes the smoothness of the surface of the resistor 2 as it is. Compared with the method of directly forming a resistor on the surface of the body by printing, the smoothness of the surface of the resistor 2 can be remarkably enhanced, and a resistance substrate having excellent resistance characteristics can be provided.

However, the adhesion between the resistor 2 and the electrode 3 and the molded body 8 depends only on the binding between the binder resin and the molten resin of the resistance paste or the silver paste.
If the adhesion is insufficient, there is a problem that when the release film 1 is peeled from the molded body 8, the resistor 2 and a part of the electrode 3 are peeled together with the release film 1. Such a problem is not limited to the resistance substrate 9 using the resistor 2 and the electrode 3 as a conductive pattern, and is the same for other wiring substrates using a fixed contact and a continuous pattern as a conductive pattern, for example. I can say that.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a method of manufacturing a wiring board which can satisfactorily transfer a conductive pattern.

[0007]

In order to achieve the above object, the present invention provides a method for producing a wiring board, wherein a conductive pattern printed on a film is transferred onto the surface of a molding resin, the method comprising: After the conductive pattern is formed by printing, an adhesive ink containing a first resin that melts at the melting temperature of the molding resin, a second resin that does not melt and an inorganic filler is applied on the conductive pattern, and then the film is coated. At least a part of the mold is loaded so as to be accommodated in a cavity, the molten resin is filled in the cavity, the molten resin is cooled, the conductive pattern is adhered to the molding resin, and the film is integrated. After that, the conductive film is transferred to the molding resin via the adhesive ink by peeling off the film. .

[0008]

As described above, in the present invention, after the adhesive ink is applied on the conductive pattern printed on the film, the film is sent to the mold and the molten resin is injected into the mold. The adhesive ink is composed of two types of resins having different melting temperatures depending on the size of the molecular weight, such as a low molecular weight epoxy resin and a high molecular weight epoxy resin, and an inorganic filler, a solvent or an additive added to the main agent. It Since the low molecular weight epoxy resin closely crosslinks and cures when the adhesive ink is heated and cured, it imparts heat resistance to the adhesive ink, that is, a function that the adhesive ink does not flow unnecessarily due to the high temperature molten resin from which the adhesive ink is ejected. Since the molecular weight epoxy resin does not tightly crosslink and harden, it exhibits a function of being softened and melted by a high temperature molten resin to achieve good adhesion with the molten resin. Further, the inorganic filler functions to adjust the viscosity of the adhesive ink during softening and melting and prevent excessive flow. Therefore, due to the characteristics of the two kinds of resins having different molecular weights contained in the adhesive ink and the inorganic filler,
The thermal behavior at a predetermined temperature can be controlled, and since the adhesive ink is interposed between the conductive pattern and the molding resin, the conductive pattern can be reliably transferred to the molding resin when the film is peeled from the molding resin. .

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view showing a schematic process of a resistance substrate according to an embodiment of the present invention, and the portions corresponding to those in FIG. 4 are designated by the same reference numerals. First, a resistance paste in which carbon powder is mixed in a binder resin is printed on one surface of a release film 1 as shown in FIG. 1A, and a solvent contained in the resistance paste is volatilized and dried, Release film 1
A resistor 2 as shown in FIG. 1B is formed on one surface of the.
Next, a silver paste in which a silver powder is mixed in a binder resin is printed on both ends of the resistor 2, and the solvent contained in the silver paste is volatilized and dried, as shown in FIG. 1 (c). After forming the electrodes 3 on both ends of the resistor 2, these are heat-cured. Furthermore, on the resistor 2 and the electrode 3,
As shown in FIG. 1D, an adhesive ink containing a low molecular weight first resin, a high molecular weight second resin, and an inorganic filler is printed, and then the solvent contained in the adhesive ink is heated. The adhesive layer 4 is formed by volatilization and curing.

Subsequently, the carrier film on which the resistor 2, the electrode body 3 and the adhesive layer 4 are formed is sent to an injection molding die 5 shown in FIG. 1 (e), and the injection molding die 5 is clamped. The molten resin is injected from the gate 6 into the cavity 7 and cooled. After that, the injection molding die 5 is opened, and as shown in FIG. 1 (f), the molded body 8 in which the molten resin is cooled and solidified, and the carrier film and the molded body 8 integrated with the laminate are formed. Obtain a laminate. Finally, when only the release film 1 is peeled from this laminate,
As shown in (g), the resistance substrate 9 in which the resistor 2 and the electrode 3 are transferred to the molded body 8 via the adhesive layer 4 is obtained.

As the release film 1, a polyester film whose surface is treated with silicon or acrylic, a polyimide film or a polyphenylene sulfide film which is not subjected to surface treatment is preferably used.

Further, as the binder resin in the paste for forming the resistor 2 and the electrode 3, thermosetting resin such as epoxy resin, phenol resin, polyester resin, acrylic resin is used, and the conductive material is, for example, resistance. Carbon black or graphite is used for the body, and silver is mainly used for the electrodes. The thermosetting resin is used as the binder resin because the coating film is strong, has high heat resistance, is hard to be damaged by the molten resin, and has a stable environmental property in the resistor. is there.

As the adhesive ink, a first resin which is not melted by the heat (melting temperature) of the molten resin injected after the adhesive layer is formed, for example, a low molecular weight epoxy resin, and a second resin which is melted at the melting temperature, For example, it is a mixture of a high molecular weight epoxy resin, an inorganic filler, a curing agent, a solvent, and an additive. Here, a bisphenol A type epoxy resin having a molecular weight of 340 to 500 is preferably used as the low molecular weight epoxy resin, and a bisphenol A type epoxy resin having a molecular weight of 1000 to 5000 is preferably used as the high molecular weight epoxy resin. As the inorganic filler, for example, glass powder, alumina, silica, etc. are used, and the particle size thereof is preferably 1 to 50 μm, and particularly, the particle size of 10 to 30 μm is optimally used. When used, the transparency of the adhesive ink is good, and the outer shape of the adhesive layer cannot be clearly recognized in the product, so that a clean impression can be given. The particle size of the inorganic filler is
If it is less than the above range, the effect of preventing excessive flow of the adhesive ink becomes small, and if the particle size is large, the coating performance of the adhesive ink deteriorates. Furthermore, as the curing agent, aliphatic amine-based, aromatic amine-based, imidazole-based, various latent curing agents and the like are preferably used, and as the solvent,
Examples include carbitol, carbitol acetate, isophorone, and the like.

Further, a thermoplastic resin is used as the molding resin, for example, PCT (polycyclohexanedimethylene terephthalate), PEI (polyetherimide), PPS (polyphenylene sulfide), PA6.
Examples thereof include T (polyamide 6T), PMMA (polymethylmethacrylate) and ABS.

In the above-mentioned embodiment, when the release film 1 is peeled from the molded body 8, the adhesive force of the adhesive layer 8 can be used to reliably transfer the resistor 2 and the electrode 3 to the molded body 8. . That is, since the low molecular weight epoxy resin contained in the adhesive ink is closely crosslinked and cured when the adhesive ink is heat-cured, the adhesive ink has heat resistance, that is, it does not flow more than necessary due to the high temperature molten resin from which the adhesive ink is ejected. On the other hand, since the high molecular weight epoxy resin is not tightly crosslinked and cured, it exhibits a function of being softened and melted by the high temperature molten resin to achieve good adhesion with the molten resin. Further, the inorganic filler adjusts the viscosity of the adhesive ink during softening and melting, and functions to prevent excessive flow. Therefore, depending on the characteristics of the two kinds of resins contained in the adhesive ink having different molecular weights and the inorganic filler, The thermal behavior at temperature can be controlled. In particular, in the injection molding die 5, the temperature distribution inside the cavity 7 is non-uniform, and the temperature becomes low when it is separated from the gate 6. However, in the above-mentioned embodiment, the adhesive ink excessively melts in the high temperature portion near the gate 6. It can be prevented from flowing and the adhesive ink can be melted to an extent necessary for adhesion in a low temperature portion away from the gate 6. Therefore, by changing the mixing ratio of these low molecular weight epoxy resin and high molecular weight epoxy resin and inorganic filler components contained in the adhesive ink,
It is possible to form an adhesive layer that can be transferred to molding resins having various melting temperatures.

Next, a specific example of the present invention will be described with reference to FIG. (Specific Example 1) First, a 75 μm polyphenylene sulfide film was used as the release film 1 shown in FIG. 1 (a), and at least one or more layers of thermosetting carbon-based resistance ink (for example, epoxy resin carbon black, Graphite (dispersed graphite) was screen-printed and heat-cured to form resistor 2 on release film 1 as shown in FIG. 1 (b). Then, as shown in FIG. 1 (c), a thermosetting silver-based electrode ink (eg, epoxy resin with silver dispersed) thereon.
Was screen-printed and heat-cured to form an electrode 3. Further, an adhesive ink prepared by the following composition and manufacturing method was screen-printed on the resistor 2 and the electrode 3, and this was heat-cured to obtain the adhesive ink shown in FIG.
The adhesive layer 4 was formed as shown in FIG. [Composition of adhesive ink] Low molecular weight epoxy resin 5 parts by weight (molecular weight 380 bisphenol A type epoxy resin) High molecular weight epoxy resin 5 parts by weight (molecular weight 3000 bisphenol A type epoxy resin) Inorganic filler 30 Vol% (glass powder particle size 15 μm irregular shape) ) Curing agent ... Aromatic amine Solvent ... Carbitol [Production method] The above materials are mixed in the above composition and dispersed by a crusher to adjust. Next, the carrier film thus produced is attached to the injection molding die 5 as shown in FIG. 1 (e), and after the injection molding die 5 is clamped,
PCT was injected as a molten resin from the gate 6 into the cavity 7 and cooled. The melting temperature of this PCT is 28
It is 5 ° C. After that, the injection molding die 5 is opened, and as shown in FIG. 1 (f), the molded body 8 in which the molten resin is cooled and solidified, and the carrier film and the molded body 8 integrated with the laminate are formed. Obtain a laminate. Finally, when only the release film 1 is peeled from this laminated body, the resistor 2 and the electrode 3 are attached to the molded body 8 as shown in FIG. 1 (g).
To obtain a resistance substrate 9 having a smooth surface.

FIG. 2 shows the composition of the adhesive ink and the transfer state of the conductive pattern (resistor 2 and electrode 3) including the above specific example 1 when the molding resin is PCT. The evaluation of the transfer state was performed as follows. First, the resistance substrate 9
After confirming that the resistor 2 and the electrode 3 are all transferred, the adhesive tape is attached to the surface of the resistor substrate 9 in accordance with the method defined in "JIS K 5400 Coating film adhesion test". After that, when the adhesive tape was peeled off, the presence or absence of the resistor 2 and the electrode 3 attached to the adhesive tape was visually observed. The quality of transfer is mainly due to the adhesive strength of the adhesive layer, so the next evaluation is as follows.
I went to the point. In the vicinity of the gate 6, the temperature and pressure of the injected molten resin are the highest, so the adhesive layer 4 excessively melts and flows, so that it cannot contribute to the adhesion between the resistor 2 and the electrode 3 and the molded body 8. If it is unevenly distributed, the transfer will not be performed well, and therefore the state of transfer can be judged by observing this part.

In the vicinity of the edge of the substrate away from the gate 6,
When the temperature of the molten resin to be injected is lower than that near the gate 6 and the adhesive layer 4 is insufficiently melted and the adhesive force is not sufficient, the resistor 2 and the electrode 3 are peeled off together with the release film 1 and transfer failure occurs. And so on. Therefore, by observing this portion, it is possible to judge the transfer situation.

The above two points were checked, and when both were good, the transfer was good, and when either one was not good, the transfer was good. Further, when no transfer of the resistor 2 and the electrode 3 was observed immediately after the resistance substrate 9 was manufactured, it was evaluated as transfer failure x.

(Specific Example 2) First, a 75 μm polyimide (PI) film is used as the release film 1 shown in FIG. 1 (a), and at least one or more layers of thermosetting carbon-based resistance ink (for example, epoxy) is used. A resin 2 in which carbon black and graphite are dispersed) was screen-printed and heat-cured to form a resistor 2 on the release film 1 as shown in FIG. 1 (b). Then, as shown in FIG. 1 (c), a thermosetting silver-based electrode ink (eg, epoxy resin with silver dispersed) thereon.
Was screen-printed and heat-cured to form an electrode 3. Further, an adhesive ink prepared by the following composition and manufacturing method was screen-printed on the resistor 2 and the electrode 3, and this was heat-cured to obtain the adhesive ink shown in FIG.
The adhesive layer 4 was formed as shown in FIG. [Composition of adhesive ink] Low molecular weight epoxy resin 7 parts by weight (molecular weight 340 bisphenol A type epoxy resin) High molecular weight epoxy resin 3 parts by weight (molecular weight 5000 bisphenol A type epoxy resin) Inorganic filler 40 Vol% (alumina powder particle size 10 μm irregular shape) ) Curing agent ... Imidazole Solvent ... Carbitol acetate [Production method] The above materials are mixed in the above composition and dispersed by a crusher to adjust. Next, the carrier film thus produced is attached to the injection molding die 5 as shown in FIG. 1 (e), and after the injection molding die 5 is clamped,
PEI as a molten resin was injected from the gate 6 into the cavity 7 and cooled. The melting temperature of this PEI is 35
It is 0 ° C. Thereafter, the injection molding die 5 is opened, and as shown in FIG. 1 (f), the molded body 8 in which the molten resin is cooled and solidified, and the carrier film 1 and the molded body 8 integrated with the laminated body are formed. To obtain a laminated body of. Finally, when only the release film 1 is peeled off from this laminate, as shown in FIG.
As shown in (1), the resistor 2 and the electrode 3 were transferred to the molded body 8 via the adhesive layer 4, and the resistance substrate 9 having a smooth surface was obtained.

FIG. 3 shows the composition of the adhesive ink including the specific example 2 and the transfer state of the conductive pattern when the molding resin is PEI. The transfer state was evaluated in the same manner as described above.

As is clear from the above results, the mixing ratio of the low molecular weight epoxy resin, the high molecular weight epoxy resin and the inorganic filler in the adhesive ink and the transfer result show a certain degree of regular transition, so that at a predetermined molding temperature. The other condition can be easily determined by setting one condition depending on which of the mixing ratio of the low molecular weight epoxy resin and the high molecular weight epoxy resin or the amount of the inorganic filler added.

The above embodiments and specific examples have been described for the case where the present invention is applied to the resistance substrate 9 having the conductive pattern composed of the resistor 2 and the electrode 3, but the present invention is not limited to this. For example, it can be applied to a wiring board using a fixed contact as a conductive pattern and a wiring pattern continuous to the fixed contact.

[0024]

As described above, according to the present invention,
Since the conductive pattern printed on the film can be surely transferred to various molding resins via the adhesive ink, it becomes possible to provide a wiring board having a smooth surface.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a manufacturing process of a resistance substrate according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a composition of an adhesive ink and a transfer state of a conductive pattern according to a specific example of the present invention.

FIG. 3 is a diagram showing a composition of an adhesive ink and a transfer state of a conductive pattern according to another example of the present invention.

FIG. 4 is an explanatory view showing a manufacturing process of a resistance substrate according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Release film (film) 2 Resistor (conductive pattern) 3 Electrode (conductive pattern) 4 Adhesive layer 8 Molded body 9 Resistive substrate (wiring substrate)

Claims (1)

[Claims] 1. A method for manufacturing a wiring board, wherein a conductive pattern printed on a film is transferred onto a surface of a molding resin, the conductive pattern is printed on one side of the film, and then the molding is performed on the conductive pattern. An adhesive ink containing a first resin that melts at the melting temperature of the resin, a second resin that does not melt and an inorganic filler is applied, and then the film is loaded so that at least a portion of the film is accommodated in the cavity of the mold. After filling the cavity with the molten resin, the molten resin is cooled to bond the conductive pattern to the molding resin and integrate the film, and then the film is peeled off to form the molding resin. A method of manufacturing a wiring board, wherein the conductive pattern is transferred via the adhesive ink.